feat: lyrics tab (#113)

[joelkanyi]

Closes #113.

Picks up @AntonioSanFer's POC fork (the first commit on this branch, authored by them) and finishes it on top of #106 so it actually runs on current main.

What this adds

A dedicated lyrics screen reachable from the expanded player, with synced highlighting, click-to-seek, and online search fallback.

Where to find it: when the player sheet is expanded, the lyrics icon sits in the bottom control row (next to repeat / queue / shuffle). Tapping it collapses the sheet and opens the lyrics screen, with the mini-player still visible at the bottom for control.

Trigger in expanded player	Lyrics screen with active line

Behavior

• Synced lyrics: lines highlight in time with the player using the LRC timestamps. The active line auto-scrolls into view at roughly one-third from the top. If you scroll manually, auto-scroll pauses until the playing line drifts out of the visible third again.
• Click-to-seek: tap any line and the player jumps to that timestamp.
• Unsynced lyrics: if the LRC isn't synced, lines render as a plain list with an unsynced chip in the header. No auto-scroll, no highlighting.
• No lyrics on server: shows a "No lyrics available" state with a Search online button that hits the /plugins/lyrics/search plugin endpoint. The error message stays visible for 5 seconds then clears.
• Auto-search online: if the user has enabled the useLyricsPlugin preference plus lyricsAutoDownload, the screen will automatically hit the plugin search endpoint when local lyrics are missing. If lyricsOverrideUnsynced is on, it'll also override unsynced local lyrics with a synced version from a plugin source.

What's in the diff

From @AntonioSanFer's POC (commit 87591c4):

• DTOs: LyricsDto, LyricsLineDto, LyricsCheckDto, LyricsRequestDto, PluginLyricsRequestDto, PluginLyricsResultDto
• Domain: Lyrics, LyricsLine
• Repository: LyricsRepository interface + DataLyricsRepository implementation (/lyrics, /lyrics/check, /plugins/lyrics/search)
• Hilt module wiring
• LyricsScreen composable (header with album art and back nav, synced/unsynced/empty body composables)
• LyricsViewModel with line index calculation, scheduled advance, online search
• LyricsUiState, LyricsUiEvent
• Three lyrics preferences in AppSettings (plugin enabled, auto-download, override-unsynced)
• Navigation wiring: gotoLyrics() on CommonNavigator / CoreNavigator, LyricsScreenDestination in NavGraphs
• NetworkApiService endpoints

Follow-up commit (cafe172):

• Move the lyrics icon into AnimatedPlayerSheet's control row. The POC modified NowPlaying.kt which isn't the active screen post-player: Add Player Animations #106, so the icon was invisible. Tap now collapses the sheet to partial then navigates so the lyrics screen is actually visible.
• Fix the position-math bug in LyricsScreen: was passing seekPosition * 1000 (a 0..1000 fraction) where milliseconds were expected, so the highlight never moved past line 0. Multiply by track.duration too.
• Change LyricsLineDto.time from Long to Double. The server returns fractional ms like 128021.99999999999 which Gson refused to parse into Long and killed every fetch. Mapper truncates back to Long for the domain model.
• Drop the 300ms look-ahead in scheduleNextLine. Lines now advance at the actual line timestamp, which matches the audio for tracks with good LRC data.
• Add statusBarsPadding() to the lyrics header so the back button and track info aren't covered by the system bar.
• Replace deprecated Icons.Default.ArrowBack with Icons.AutoMirrored.Filled.ArrowBack.

Testing

Tested on a Pixel 7 Pro running the build from this branch:

• Loaded synced lyrics across multiple tracks. Highlight advances on the line's timestamp within ~100ms.
• Click-to-seek: works, player jumps and highlight catches up.
• Switching tracks while on the lyrics screen: state resets, new lyrics load.
• Back navigation: returns to the previous screen with the mini-player still visible.
• Header reads cleanly below the status bar, back button tappable.

One sample track (Short N Sweet by Nyashinski) had LRC timestamps roughly 2 seconds ahead of the actual sung audio. Every other track lined up, which points to bad data in that one LRC file rather than a sync issue in the code. The sync trace logs I ran during dev confirmed advances fire at the exact timestamps the LRC declares.

Known follow-ups (out of scope for this PR)

• Settings UI for the three lyrics preferences. The preferences exist in AppSettings/AppSettingsRepository but there are no toggles in the settings screen yet, so they default to off.
• Per-track lyric offset adjustment. For LRC files like the Nyashinski one where the data is offset from the audio, a manual ±n seconds adjustment would let the user fix sync without us changing the data.
• The "Go to album" / "Go to folder" navigation from the lyrics header onClick-artist is wired but there's no parallel for clicking the title or thumbnail. Minor.

Credit

Lyrics architecture, DTOs, repository, ViewModel sync logic, and the initial LyricsScreen composable are @AntonioSanFer's work from https://github.com/AntonioSanFer/android/tree/feature/lyrics. The follow-up commit on this branch is the integration glue and a handful of bug fixes spotted while testing.

[CLAassistant]

All committers have signed the CLA.

[AntonioSanFer]

Everything seems great, and working 👍

[Ericgacoki]

👁️